Re: New Xen boot infrastructure proposal

[David Vrabel <david.vrabel@citrix.com>]

On 21/05/13 11:36, Daniel Kiper wrote:
> Hey guys,
> 
> Here are my thoughts about current Xen boot
> infrastructure and some changes proposal.
> It is linked with EFI development but not only.
>
> [...] It means
> that at this stage it is worth to create completely new
> boot structure which is not linked so tightly with any boot
> protocol. It should contain all needed stuff, be architecture
> independent as much as possible and easily extensible.

It's not clear how a new set of structures like this fits the
requirement to be easily extensible.  Aren't you going to have the same
problems if new fields need to be added?

I would suggest considering a linear block of (type, length, data)
tuples for each field.  That way only the needed/applicable fields can
be included, and Xen can easily skip over field it does not recognize or
care about (so new fields can be added without breaking compatibility).

> In cases when architecture depended things are required
> there should be special substructure which would contain
> all required stuff. More or less it should look like in x86 case:
> 
> /* Xen Boot Info (XBI) module structure. */
> typedef struct {
>   u64 start;
>   u64 end;
>   char *cmdline;
> } xbi_mod_t;
> 
> /* Xen Boot Info Arch (XBIA) memory map structure. */
> typedef struct {
>   /*
>    * Amount of lower memory accordingly to The Multiboot
>    * Specification version 0.6.96.
>    */
>   u32 lower;
>   /*
>    * Amount of upper memory accordingly to The Multiboot
>    * Specification version 0.6.96.
>    */
>   u32 upper;
>   u32 map_size;
>   struct e820entry *e820map;
> } xbia_mem_t;
> 
> /* Xen Boot Info Arch (XBIA). */
> typedef struct {
>   EFI_SYSTEM_TABLE *efi_system_table;
>   u64 mps; /* Pointer to MPS. */
>   u64 acpi; /* Pointer to ACPI RSDP. */
>   u64 smbios; /* Pointer to SMBIOS. */
>   xbia_mem_t mem;
>   struct xen_vga_console_info vga_console_info;
>   struct edd_info *edd_info;
> } xbia_t;
> 
> /* Main Xen Boot Info (XBI) structure. */
> typedef struct {
>   char *boot_loader_name;
>   char *cmdline;
>   u32 mods_count;
>   xbi_mod_t *mods;
>   xbia_t arch;
> } xbi_t;

David